Method for photogravures



Patented June 3, 1930 UNITED STATES PATENT oFFicE LEONARD finalise, or ST. LOUIS, mrssooar, ASSIGNOR or ONE-THIRD TO BEN v. ZILL- MAN, OF sr'LoUIs, MISSOURI METHOD FOR PHOTOGRAVURES Ii'o Drawing.

My invention relates to improvements in the art of photo-gravure and more specifically to certain of the steps in the develop ment thereof.

One of the objects of my invention is to so improve the method of the development of the carbon-tissue used in said process, that the time necessary for this work will be cut down to approximately one-third of that now required. 7

Another object of my invention is to provide a process for developing the carbontissue, whereby a'unif'orm and highly pre ferred print will always be produced, this 5 print being sharpand clear, and not muddy or having any tendency to run in hot weather.

Another object of my invention is to provide'a process of the kind described, wherein the ingredients used will be fairly cheap,

'20 easily obtainable, and of such character that but little of said ingredients will be required for the carrying out of the process.

Many other objects and advantages of the process herein shown and described will be '25 obvious to those skilled in the art to which this invention appertains, from the disclosures herein given.

To this end, my invention consists in the novel method or procedure herein described, so and the materials used therein, and more particularly pointed out in the claims.

Photo-gravure, which is sometimes called by other terms,'such as Roto-gravure and the like, is distinguished from the ordinary or photo-engraving process in that in the former the images produced on the plate for reproduction through printing, are in intag Application filed August 17, 1927. Serial No. 213,709.

thereafter, is placed over the positive and exposed. This carbon-tissue has been long in use in photography and is merely a pure gelatine, preferably colored or pigmented and which has been deposited evenly and uniformly onto a sheet of suitable paper, this paper being termed the backing sheet. This gelatine actually enters into the pores or grain of the paper backing sheet and it is impossible to remove the same by separation from the tissue when the tissue is in a dry state.

The next step in the process is to affix the exposed carbon-tissue onto the printing cylinder so that the development and the etching may be successively done. ing cylinder, which in newspaper work (to which this invention is chiefly directed)v may be up to six feet or so in length and up to 13 inches in diameter, and which in this size weighs approximately a ton, is placed upon a carrying frame so it may be rotated for handling; This cylinder has been scrupulously cleaned and polished, and the carbon tissue, just exposed in the method described, is properly registered or aligned on the surface of the cylinder, for securement thereto.

This print ater is then applied between the opposed surfaces of the tissue and the cylinder, and

pressure then exerted onto the back of the tissue to press the same onto the roll to cause the tissue to stick tightly to the roll, after which anyexcess water is wiped off the back of the tissue. Inasmuch as several pieces of tissue may be aflixedto the same roll, precaution must be taken that one of the tissues will not be developed more than the others,

and for this reason all of the moisture, or

nearly so, is removed from the tissue in some suitable manner, as by blowing air thereon,

tissue and saturating the same until the water soaks through the pores or grain of the paper to reach the gelatine to sufficiently soften the same so that the backing may be pulled off, but this separation or peeling can not take place until the heavy cylinder has been heated to a fairly high degree of heat (approximately 115 Great care must be taken in this work to judge the earliest time at which the backing may be peeled, because if there are any hard spots or a slight amount of oil or grease on the tissue, the water will not penetrate these spots as rapidly as the other portions, and therefore if the gelatine at these spots is not softened, the gelatine thereat will pull off together with the backing, which necessarily means that these torn places in the gelatine must be replaced, and in certain cases the new tissue applied and the entire work done over.

After the backing sheet has been removed, the hot water is further applied to the film of gelatine to complete its development, inasmuch as very little of the development of the film has been done before the paper backing sheet has been removed, because the water had no free access to the gelatine, but had to soak through the paper backing.

After the development has continued to the desired stage, the cylinder is then cooled, generally by applying cold water thereto, and then a faster-drying medium such as alcohol, after which the cylinder (with the completely developed gelatine thereon) is dried and further cooled by blowing air thereonto.

. From the description hereinbefore described it will be readily seen that much valuable time lost, first, in heating up the cylinder to such a point Where the gelatine is sufficiently soft to permit the peeling off of the backing, and second, in cooling down the cylinder to such a temperature that further treatment may be given it, this lost working time amounting to approximately a half hour or more where the large-sized cylinders are handled.

After cooling, the cylinder may be further treated, as by painting out those portions of the film that are not to be etched, after which 'the cylinder can be placed in the etching solution.

After being etched, the cylinders are mounted in the press in their ink tanks, and the print-paper webbed through the press so that it passes over the cylinders and absorbs the ink from the etched portions.

In the new method, after the carbon-tissue is affixed to the cylinder and the excess moisture removed and the tissue dried, hot water is not copiously applied, but, upon the contrary, instead of depending upon hot water to soak through the paper backing to soften the gelatine before separation of the paper backing sheet can be effected, I use a liquid chemical compound, one of whose ingredients is such that it will practically instantaneously penetrate through the backing sheet, and I then immediately apply hot Water to the sheet, this hot water going through the open pores of the paper without hindrance to quickly soften the gelatine that is unexposed, so that the backing sheet may be readily peeled off, after which the development is completed with hot water. The penetrating ingredient that I have found highly suitable for the purpose is a hydrocarbon solvent, one of the light-boiling liquid fractions of coal tar, as for example benzole, this chemical having the characteristics of being able to instantly break through the paper backing sheet to soften only the unexposed portions of the gelatine, so as not to damage the print, and having practically little reaction with the exposed portions of the gelatine. The hot water is enabled to immediately reach those portions of the gelatine that areimbedded in the pores or grain of the sheet to soften them, and consequently it is apparent that a very much smaller amount of hot water is required for this purpose of soaking off the backing, than with the old method of relying solely upon hot water. Therefore the cylinder will not be heated up to any appreciable extent and need not be left standing idle while waiting for it to cool down to proper working temperature after the developing has been completed.

I also have an ingredient in my compound, that will act as a hardener of the gelatine to thereby overcome any tendency of the gelatine to become cloudly or run in hot weather especially, this ingredient also acting to retard the developing action of the other ingredients. A material that I have found highly eflicient for this purpose is acetone.

Inasmuch as the ingredients previously described are quite often found to contain impurities such as grease, it is preferable that a rectifier be embodied in the compound, which shall serve to overcome these impurities, and for this purpose I have found alcohol, preferably pure grain alcohol, highly suitable for the purpose.

In compounding the various igredients to make up the solution, it is preferable to mix them in the following order and in approximately the following proportions by volume:

1 to 2 parts of alcohol.

1 part of acetone.

8 parts of benzole.

If any grease or impurities separate out of the solution, the clear liquid may be siphoned or otherwise removed and put up for use.

At different times of the year it may be found desirable to slightly vary the proportions used in making up the solution, which may be termed a pre-developing compound, but these slight changes are merely for ease in mixing and handling and have no marked effect as to their actions on the carbon-tissue.

Having thus described my invention, it is obvious that various immaterial modifications may be made in the same Without departing from the spirit of my invention;

hence I do not Wish to be understood as limiting myself to the exact proportions and ingredients used and the method of carrying out this invention as described, except as limited by the claims. I

What I claim as new and desire to secure by Letters Patent is:

1. That step in the art of photo-gravure consisting of applying a benzole-containing liquid to the back of the carbon tissue for penetrating through the paper backing sheet of the carbon-tissue previous to developing the same with water, to thereby reduce the time required for the separation of the backing sheet and the gelatine thereon.

2. That step in the art of photo-gravure consisting in saturating the backing sheet of the carbon-tissue with a benzole-containing liquid to thereby rapidly open the pores of said tissue immediately prior to the regular development with water.

Steps in the process of developing carbon-tissue, consisting in applying benzolecontaining liquid to the back of said tissue, then immediately applying hot water thereto, then peeling 0H said back, and then continuing the development of the tissue with water. i

at. A compound for predeveloping carbontissue, comprising benzole and acetone.

5. A compound for pre-developing carbon tissue, comprising approximately eight parts of benzole and one part of acetone.

6. A compound for pre-developing carbontissue, comprising approximately eight parts of benzole, one part of acetone, and from one to two parts of alcohol.

7 A compound for pre-developing carbon tissue, comprising alcohol, acetone and ben zole.

LEONARD HUGHES. 

